1. Field of the Invention
The present invention relates to a secondary battery, and more particularly, a safety apparatus for a secondary battery and a secondary battery having the same.
2. Description of the Related Art
Secondary batteries are generally rechargeable and can be made into a smaller size with high capacity. Typical examples of secondary batteries include nickel-metal hydride (Ni-MH) batteries, lithium (Li) batteries and lithium ion (Li-ion) batteries.
Secondary batteries are classified into cylindrical batteries using a cylindrical aluminum can, rectangular batteries using a rectangular aluminum can, and pouch type batteries accommodated in a thin-film pouch type casing, according to the outer appearance of a casing accommodating a power generating element, that is, an electrode assembly.
A need exists in secondary batteries for a safety device that automatically shuts operation of a battery down when the battery is not operating normally. For example, an internal or an external short circuit in a secondary battery can lead to overheating of the battery and a build up of pressure in the battery. Without the presence of a safety device, the battery would continue to overheat and reach excessive pressures until the battery explodes. In order to prevent such a dangerous explosion, safety devices are used to stop the battery from generating power when the battery starts to act abnormally but before the battery explodes.